1. Field of the Invention
This invention relates an atmospheric pressure method for the production of free flowing particles of Wegscheider's Salt (Na.sub.2 CO.sub.3.3NaHCO.sub.3) of low bulk density from anhydrous sodium carbonate or light ash.
2. Description of the Prior Art
The production of alkali products containing Na.sub.2 CO.sub.3 and NaHCO.sub.3 in various weight ratios is well known in the prior art.
Co-pending application U.S. Pat. No. 4,151,266 (Robey et al.), filed June 22, 1978 discloses a single stage, superatmospheric method for the production of free-flowing particles of Wegscheider's Salt (Na.sub.2 CO.sub.3.3NaHCO.sub.3) of low bulk density from particles of anhydrous sodium carbonate of high bulk density.
Co-pending application Ser. No. 099,678 filed Dec. 3, 1979 describes a process for producing a unique Wegscheider's Salt product from sodium carbonate monohydrate wherein the monohydrate particles are contacted with a gaseous mixture containing carbon dioxide and water at atmospheric pressure. The product so produced is composed of Wegscheider's Salt needles oriented within the hexagonal crystal form of the monohydrate and has excellent flow properties. The disadvantage of this process is its requirement to employ the monohydrate as a starting material. A similar process is described in application Ser. No. 356,663 employing sodium sesquicarbonate as the starting material with a corresponding difference in the Wegscheider's Salt product. Although the product produced from the sesquicarbonate has good absorbtivity and low bulk density, the flow properties are unacceptable for certain commercial uses.
British Pat. No. 206,372 describes a process of treating sodium carbonate with a gaseous mixture of carbon dioxide and water at temperatures from 90.degree.-100.degree. C. to produce Wegscheider's Salt and U.S. Pat. No. 1,583,661 discloses a similar process to produce Wegscheider's Salt product composed of thin, elongated needlelike particles. In both cases the bulk density and flow properties of the product are poor.
U.S. Pat. No. 3,701,737 discloses a process of contacting sodium carbonate, sodium monohydrate or mixtures thereof with water to produce wet agglomerates; the temperatures of the charge and water are maintained above 35.degree. to 109.degree. C. to avoid the formation of the hepta- and decahydrate of sodium carbonate and to maintain free-water in the agglomerates. The wet agglomerates are subsequently treated with sufficient CO.sub.2 at atmospheric pressure to obtain carbonated agglomerates of NaHCO.sub.3 and Na.sub.2 CO.sub.3 in molar ratios of 0.4:1 to 1.5:1. These carbonated agglomerates may be calcined, as described in U.S. Pat. No. 3,695,831, to form absorptive soda ash.
A process of hydrating light ash is disclosed in U.S. Pat. No. 3,719,745 wherein the free-flowing hydrated particles so produced are carbonated to saturation and thence calcined to produce low density sodium carbonate.
Due to the present environmental efforts to reduce or eliminate the phosphates present in detergents, there is a need for a product having mild alkalinity, low bulk density, low friability, good flow properties and high absorbancy of liquid surfactants. The Wegscheider's Salt compositions of Ser. No. 778,301 fill this need, and it would be desirable to produce such from commercially available soda ash.
It is accordingly one object of the present invention to provide a method for the production of an absorptive, low bulk density, alkaline material with low friability and good flow properties.
It is a further object of the invention to provide an atmospheric pressure process for converting a commercially available reactant, namely anhydrous sodium carbonate or light ash having a bulk density less than about 750 g/l into the free-flowing, alkaline Wegscheider's Salt described in Ser. No. 778,301.
These and other objects will be apparent from the description which follows.